Hydraulic fluids



Patented Feb. 5, 1946 UNITED STATES PATENT- OFFICE HYDRAULIC FLUIDS Rupert 0. Morris, Berkeley, Edward C. Shokal,

Oakland, and Alva V. Snider, Richmond, Calii., assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application July 31, 1943,

Serial Ida-497,136

v 16 Claims. The present invention relates to compositions of matter and more particularly to fluids for use Variousproposals have previously been made involving the use of mixtures of alcohol and castor oil, glycerine and the like as hydraulic power transmission media in systems such as those mentioned above. In a great number of such previously proposed fluids, however, there have been practical disadvantages such as, for

tions. Other objects, together with some of. the

advantages to be derived in practicing the invention, will become apparent in the following specification in which the preferred details and embodiments thereof are described.

Hydraulic fluids prepared according to the present invention have been found to meet the great majority of essential requirements for such materials, i. ,e. they are non-corrosive in action on most metals, non-hygroscopic, and non-toxic; they have high heat stability, high flash points and satisfactorily low pour points; they are sumciently compatible with mineral, animal and vegetable oils for most practical purposes and are relatively non-deleterious in their action on both natural and synthetic rubbers. Further, they may be easily and inexpensively manufactured in large quantities from available raw materials.

According to the instant invention, improved hydraulic fluids are prepared by employing as (or incorporating as an ingredient of) a hydraulic fluid a sulfolane or a-sulfolene. The compound suliolane has.the structural formula:

The compound a-sulf'olene has'the structural formula:

HC'CH:

Its derivatives are compounds wherein one or more of the hydrogen atoms is replaced by an organic radical which may contain a polar group.

nitrogen, sulfur and/or halide atoms. In hydrocarbon-substituted sulfolanes the hydrocarbon radicals may be aliphatic, alicyclic, aromatic or mixed. Sulfoiane derivatives containing oxygen include hydroxy sulfolanes, sulfolanyl-ethers, -aldehydes, -ketones, -acids and -esters; suliolane derivatives containing nitrogen include sulfolan'yl-amines, -nitriles and nitro-sulfolanes; sulfolane derivatives containing sulfur include sulfolanyl sulfides, -sulfoxides and -sulfones. Other sulfolane derivatives may contain halide radicals, inorganic esters or mixed radicals of those above mentioned, such as acid amines, halohydrins, sulfonamides, etc. To meet stability requirements, these organic substitution radicals should contain not more than one oleflnic double bond and preferably none, Derivatives'may be made by condensing a conjugated diolefin with sulfur dioxide, and then subjecting the resultant.

product to hydrogenation, alkylation, hydration, lamination, chlorination, nitration and/or other substitution or addition reactions.

Specific sulfolanes or alpha-sulfolenes which may be utilized for the purpose of the present invention include the following, among others: sulfolane, alpha-sulfolene, hydrocarbon-substituted sulfolanes and alpha-sulfolenes, such as aliphatic, alicyclic, aromatic or mixed sulfolanes, preferably containing not more than one oleflnic double bond per radical, if any, and not more than about 14 carbon atoms, e. g. methyl, ethyl, propyl, butyl, dimethyl, diethyl, methyl ethyl, etc. sulfolanes or alpha-sulfolenes; hydroxy suliolanes such as 3-sulfolanol, 2-sulfolanol, 3-methyl-4- sulfolanol, 3,4-sulfolanediol, etc.; suli'olanyl ethers such as methyl-3-, propyl-3-, allyl-3-, butyl-3-, crotyl-3-, isobutyl-3-, methallyl-3-, methyl vinyl carbinyl-3-, amyl-3-, hexyl-3-, octyl- 3-, nonyl-3-, glycerol alpha-gamma-diallyl-betaso 3-, tetrahydrofurfuryl-3-, 3,3,5-trimethylcyclohexyl-3-, m-cresyl-3-sulfolanyl ethers, corresponding 2-sulfolanyl ethers, disulfolanyl ethers, etc.; sulfolanyl esters such as 3-sulfolanyl acetate, 3-suliolanyl-caproate, -laurate, -palmitate. 56 -stearate, -oleate, -propionate, -butyrate, etc.;

ing and more specifically may containoxygen,

N-suliolanes such as S-sulfolanylamine, N- methyl-, N-ethyl, N-N-dimethyl-, N-allyl-, N- butyl-, N-octyl-3-sulfolanylamines, eta; suli'olanyl sulfides such as ethyl-3-, tertiary butyl-3-, isobutyl-3-, methallyl-3-sulfolanyl sulfides, iii-3- sulfolanyl sulfides, etc.; sulfolanyl sulfones such as methyl-3-, ethyl-3-, propyl-3-, amyl-3-suliolanyl suliones; sulfolanyl halides such as 8- chloro-, 3,4-dichloro, 3-chloro-4-methyl sulfolanes, etc.; and mixed sulfolanes such as 4- chloro-3-sulfolanol, 4-chloro-3-sulfolanyl' acetate, 3-sulfolanyl amine hydrochloride, 12(3- sulfolanyl) acetamide, etc.', alpha-sulfolenes corresponding to the above sulfolanes, etc.

Although many of the sulfolanes and alphasulfolenes noted above are admirably suited for use per se as hydraulic fluids for many applications, for general utility purposes it will often be found advantageous to admix them with organic solvents. Among the organic materials suitable for the purpose are the following: alcohols such as the mono and polyhydric, aliphatic, alicyclic, aromatic and amino alcohols, including specifically methanol, propanol, butanol, isopropanol, isobutanol, various pentanols, hexanols, octanols, diacetone alcohol, ethylene and ropylene glycol, glycerol, cyclohexanol. phenol, benzyl alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol, triethanolamine and ethoxy amino butanol; organic esters such as ethyl, propyl, butyl, etc., acetates; ethers such as di-isopropyl, di-isobutyl, ethyl tertiary butyl, methyl ricinoleyl ethers, dichlordiethyl ether, diphenyl oxide, chlorinated diphenyl oxides; monomethyl, ethyl, propyl, butyl, isobutyl, etc. ethers of ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, polypropylene glycol and diglycerine; aldehydes such as butyraldehyde, heptaldehyde and benzaldehyde fur,- fural; ketones such as methyl ethyl ketone, methyl vinyl ketone, di-isopropyl ketone and cyclohexanone; nitrogen containingjzompounds such as dimethyl formamide, ethanol formamide, octyl amine; hydrocarbons such as hexanes, heptanes, octanes, benzene, toluene, xylenes, cyclohexane, naphthas, kerosene, alkylates, gas oils, light lube oils, trimethylcyclohexane, etc.

In those instances wherein it is desirable or necessary to enhance the lubricating characteristics of the suli'olanes or to provide greater fluidity where extremes of temperature are encountered, a lubricant may be added. Suitable lubricants comprise one or more materials selected from the group consisting of animal, vegetable and mineral oils, blown animal and vegetable oils, and alcoholysis products of animal and vegetable oils and blown animal and vegetable oils. The term animal oils, for the purpose of the present specification, is intended to include-in the broad sense all terrestrial animal, marine animal and fish oils. A lubricant is preferably employed which is characterized by being a glyceride or other ester of fatty acids, and more specifically, one which contains hydroxy or unsaturated groups, or both. As specific examples, among the numerous oils which may be utilized for this purpose, the following are included: almond, blackfish, candlenut, castor, cocoanut, cod, corn, cottonseed, croton, eucalyptus, geranium, grape seed, hemp, junier, lard, lemon, linseed, mustard green, menhaden, neats-foot, olive, oiticica, orange, palm, peanut, perilla, porpoise, rapeseed, seal, sesame, shark, sperm, tallow, train, soybean, sunflower, teaseed, walnut, whale, wool and the like. Also, blown oils such as blown castor oil, blown corn oil, blown cottonseed oil, blown peanut oil and blown soyabean oil may be utilized alone or in combination with other oils and oil derivatives or both.

Derivatives of these oils which may also be utilized as lubricants in hydraulic fluids include, for example, those derivatives which may be obtained by alcoholysis of those vegetable and animal oil esters and/or blown oil esters mentioned above with a compound containing one or more hydroxyl groups capable of alcoholysis reaction. Examples of compounds suitable for this reaction include, among others, any simple alcohol or alcohol containing a functional group such as amino, keto, aldo, ether, ethylenic or other unsaturated groups and the like. Thus, for example, desirable oil derivatives may be obtained by heating a vegetable or animal oil or blown vegetable or animal oil, as previously disclosed, with such monohydric alcohols as methyl, ethyl, normal and isopropyl, butyls, amyls, hexyls, heptyls, cetyls, nonyls, decyis, dodecyl, 2-ethyl butyl and ethyl hexyl; the individual alcohol or mixture of branched chain alcohols obtainable by catalytic hydrogenation of oxide of carbon under pressure, such as 2-methyl butanol-l, 3-methyl butanol-2, 2-methyl pentanol-3, 2-methy1 pentanol-l; 2,4- dimethyl pentanol-i, 2,4-dimethyl hexanol-S, 4- methyl hexanol-l, 2,4-dimethyl hexanol-l, 4- methyl heptanol-l and the like; similarly, such dihydric alcohols and glycols may be used for alcoholysis of the oil as ethylene glycol, the 1,2- and 1,3-propylene glycols, the butylene and isobutylene glycols, the amylene and hexylene glycols, and the like, as well as polyglycols such as po ethylene glycol and dipropylene glycol.

dric alcohols such as methyl glycerine and other poly'hydric alcohols may be utilized for alcoholysis of the oils disclosed previously, as well as the trihydric alcohols which contain functional groups in addition to hydroxyl groups. Further I miscellaneous alcohols which may be utilized for alcoholysis with the animal or vegetable oils and which come within the scope oi this invention include cyclohexanol, benzyl alcohol, naphthenyl alcohol, sorbitol, furfuryl alcohol and the like. Alcohols containing amino, keto, aldo, ether, ethylenic or unsaturated groups which may be employed are hydroxy-ethylamlne, propionyl carbinol, glycolic aldehyde, glycol monomethyl ether and diethyl acetylene glycol monopropionate, which are representative respectively of alcohols containing such functional groups. All of the specific mono-, diand trihydric alcohols hereinbefore set forth are representative and illustrative of the alcohols which may be utilized accord- .ing to the present invention for the production of derivatives of animal and vegetable oils.

In the alcoholysis of vegetable or animal oils, such as previously described, these mono-, diand 'tr'ihydric alcohols, acetals or alcoholic bodies containing a hydroxyl group may be mixed with varying proportions of the vegetable or animal oils and heated, preferably to a temperature of from 50 C. to 250 C. Stoichiometric proportions of oil and alcoholic bodies necessary for the alcoholysis reaction may be employed; it is preferable, however, to use an excess of the alcoholic body ranging from 1 to. 20 times the quantity required to complete the reaction. This excess speeds up the reaction and permits its rapid completion at lower temperatures. The excess alcohol or alcoholic body may or may not be removed from the final product, as desired. It is preferable to carry out the reaction in the presence of catalysts such as, for

example, potassium oleate or ricinoleate, potassium' carbonate, potassium hydroxide, zinc oxide,

lead oxide and the like. It has been found that ingredients for the complete hydraulic fluid composition. Suflicient pressure is employed to per-' mit the use of temperatures which in turn will eilect a suitably rapid reaction rate, particularly where low boiling reactants are involved.

Solvents .or diluents and/or oils, such as described above, may be incorporated with sulfolanes in ratios varying'over a wide range. Thus, with from to 95% by volume of a sulfolane, the diluents and lubricants may be employed in proportions of 5 to 95% by volume of diluent or lubricant, or, when employing mixtures of diluents and lubricants, 5 to 95% by volume of such a mixture may be used with 5 to 95% by volume of a sulfolane or mixture of sulfolanes, the mixture of diluent and lubricant varying from 1 to 99 parts of diluent to 99 to 1 part of lubricant. For general purpose uses, however, from approximately 5 to 50% by volume of sulfolanes is incorporated with from 50 to 95% by volum of a diluent-lubricant mixture.

Additional materials may also be included in the hydraulic fluids prepared according to the present invention, if desired. For example, it will at times be found advantageous to add a small proportion of graphite either alone or in fluid suspensions, such-as those known under the tradenames of Castordag, Aquadag," Glydag," and the like, which are suspensions of graphite in castor oil, aqueous media and polyalcohol respectively. Quantities ranging from about 0.001 to 0.5% by volume of graphite based on the total fluid composition are generally satisfactory.

Although sulfolanes are generally characterized by being relatively non-corrosive with respect to most metals, if this ingredient or other ingredients with which it is blended should react slightly with metal parts of a particular hydraulic system, a small quantity of a corrosion inhibitor may be also incorporated in the composition. Typical examples of corrosion inhibitors which may be emcosity of 130 seconds Saybolt and a pour point of F.

Esample II 30 parts by volume of 2,4-dimethylsulfolane, 10 parts by volume of castor oil, 32.5 parts by volume of diacetone glycol, 25 parts by volume of propylene glycol and 2.5 parts by volume of a corrosion innhibitor. The blended composition had a viscosity of 62.8 seconds Saybolt Universal at 100; F. and a pour point of less than 65 F.

Example III 20 parts by volume of 2,4-dimethyl sulfolane, 53 parts byvolume ofdiacetone glycol, 25 parts by Universal at 100 1''.

volume of propylene glycol and 2 parts by volume of a corrosion inhibitor. The blended composition had a viscosity of seconds Saybolt Universal at 100 F. and a pour point below F.

Example IV 18.7 parts by volume of 3-sulfolanol, 30 parts by volume of castor oil, 48.7 parts by volume of diacetone glycol and2.6 parts by volume of a corrosion inhibitor. The blended composition had a viscosity of 221 seconds Saybolt Universal at 100 F. and a pour point of 40" F.

Example V Example VI 25 parts by volume of allyl 3-sulfolano1 ether, 40 parts by volume of castor 011, 32.5 parts by volume of diacetone glycol and 2.5 parts by volume of a corrosion inhibitor. The blended composition had a viscosity of 164 seconds Saybolt Universal at 100 F. and a pour point oi --40 F.

ployed for this purpose include, among others, so-

dium nitrite, calcium nitrite, borax, sodium bichromate, potassium bichromate, sodium chromate, potassium chromate, triethanolamine oleate, triethanolamine ricinoleate, sodium phosphate, potassium phosphate, sodium acid phosphate, potassium acid phosphate, salts of organic N-bases with nitrous acid, phosphoric acid, chromie acid, and the like. Satisfactory results are usually obtained by adding one or more of'the above inhibitors in amounts ranging from 0.1 to 3.0% of inhibitor by weight based on the finished hydraulic fluid composition.

The following specific examples illustrate typical hydraulic fluid which have been prepared using sulfolanes as essential ingredients of their composition:

Example I o.- diacetone glycol and 2.5 parts by volume'of an inhibitor. The blended composition had a vis- Example VII 25 parts by volume of allyl 3-sulfolanol ether, 20 parts by volume of castor oil, 53 ,parts by volume of diacetone glycol and 2 parts by volume of a corrosion inhibitor. The blended composition had a viscosity of seconds Saybolt Universal at F. and a pour point of 40 F.

Example VII] 65 parts by volume of 2,4-dimethylsuifolane, 32.5 parts by volume of dimethyl cyclohexyl carbinol and 2.5 parts by weight of a corrosioninhibitcr. The blended composition had a viscosity of 43.1 seconds Saybolt Universal at 106' F. and a pour point below 65 F.

Example IX 72.5 parts by volume of 2,4-dimethylsulfola;le, 25 parts by volume of diacetone glycol and 2.5 parts by volume of a corrosion inhibitor. The blended composition had a viscosity of 43.1 seconds Saybolt Universal at 100 F. and a pour point below 65 F.

Example X 33.5 parts by volume of tetrahydroiuriuryl alcohol, 40 parts by volume of castor oil, and 2.5 parts by volume oi a corrosion inhibitor. The blended composition had a viscosity of *.4 seconds Saybolgpniversal at 100 1". and a pour point below I".

The corrosion inhibitor used in each of the above examples comprised equal volumes of phosphoric acid and cresylic acid, the mixture or the two acids being neutralized with triamylsmine, as set forth in U. 8. Army Air Corps specification No. 8588-0 for hydraulic fluids.

Representative examples of sulfolane derivatives which were found particularly satisfactory for use in hydraulic fluids compounded for use inhvdraulic systems including rubber parts include the iollowing: 3-methylsuliolane, 2,4-dimethylsuliolane, 3-suliolanyl amine, methyl 3- suliolanyl ether, allyl a-sulfolanyl ether. tetrahydloiuriuryl a-suliolanyl ether, nonenyl 3-suliolanyl ether and glycerol alpha, gamma-diallyl beta (3 sulfolanyl) ether. These materials, when tested for swelling of rubber according to A.'S. T. M. Designation D471-37T, wereiound to be superior to a blend comprising castor oil and amyl acetate in equal volumes.

As has been pointed out previously, suliolanes and alpha suliolenes may be used by themselves as hydraulic fluids, the particular compound or mixture of compounds and amount thereof to be used in blended compositions most suitable for a particular application being determined experimentally. Factors which must be considered include whether light or heavy grade of fluid is required, one which is particularly resistant to viscosity changes over a wide temperature range, one which is compatible with particular diluents or lubricants, one which will not affect a particular type of rubber composition, one which has a particularly low vapor pressure, etc. A solubiliz ing agent may also be added, if necessary.

The hydraulic fluids of the present invention, whether comprising a sulfolane, sulfolanes, or e-suli'olenes alone or in combination with other ingredients, as described above, may be" used as fluid power transmission media in any of the common hydraulic systems wherein power is transmitted from actuable element to an actuated element by means of a fluid, the most common form of such a system comprising a pair of variable volume chambers with connecting conduit means, the chambers and the conduit means being filled with a fluid, hydraulic power transmission medium. The hydraulic fluids of the present invention may, of course, also be used in analogous equipment in which power transmission is not the primary purpose of design, as for example in power absorption systems such as damping mechanisms, shock absorbers and the like. a

We claim as our invention:

1. In homogeneous hydraulic fluids of the class described, a composition consisting of from about 20% to about 72.5% by volume of a material selected from the group consisting of sulfolanes and alpha-sulfolenes and as a balance a mixture of solvent and a material selected from the group consisting of animal, vegetable and mineral oils, blownanimal and vegetable oils, and alcoholysis products of animal and vegetable oils and blown animal and vegetable oils.

2. In homogeneous hydraulic fluids of the described, a composition consisting of from class about 20% to about 72.5% by volume of a hydrocarbon substituted sulfolane and as a balance a mixture of solvent and a material selected from the group consisting of animal, vegetable and mineral oils,

blown animal and vegetable oils, and alcoholysls products of animal and vegetable oils and blown animal and vegetable oils.

3. In homogeneous hydraulic fluids of the class described, a composition consisting of from about 20% to about 72.5% by volume of a hydroxy suli'olane and as a balance a mixture of solvent and a material selected from the group consisting of animal, vegetable and mineral oils, blown animal and vegetable oils, and alcoholysis products of animal and vegetable oils and blown animal and vegetable oils.

4. In homogeneous hydraulic fluids of the class described, a composition consisting of from about 20% to about 72.5% by volume of a sulfolanyl ether and as a balance a mixture of solvent and a material selected from the group consisting of animal, vegetable and mineral oils, blown animal and vegetable oils, and alcoholysis products of animal and vegetable oils and blown animal and vegetable oils.

5. In homogeneous hydraulic fluids of the class described, a composition consisting of approximately 25% by volume of 2,4-dimethylsulfolane,

approximately 40% by volume of castor oil, and

- scribed the combination comprising an actuating element and an actuable element, conduit means connecting said actuating element and said actuable element, and a. liquid filling in said elements and said conduit means, said liquid filling consisting of a solvent and from about 20% to about 12.5% byvolume. of a. hydrocarbon-substituted sulfolane.

- 8. In hydraulic equipment of the class described the combination comprising an actuating element and an actuated element, conduit means connectingsaidactuating element and said actuated element and a liquid filling in said elements and said conduit means, said liquid filling consisting of from about 20% to about 72.5% by volume of-a material selected from the group consisting of sulfolanes and alpha-sulfolenes, and as the balance a-mixture of a solvent and a material selected from the group consisting of animal, vegetable and mineral oils, blown animal and vegetable oils, and alcoholysis products of animal and vegetable oils and blown animal and vegetable oils.

9. Inhomogeneous hydraulic fluids of the class described, a composition consisting of from about 20% to about 72.5% by volume of a material selected from the group consistingof sulfolanes and alpha-sulfolenes and as a balance a mixture of an alcohol and a material selected from the group consisting of animal, vegetable and mineral oils, blown animal and vegetable oils, and

and blown animal and vegetableoils.

10. The fluid of claim 9 wherein said alcohol is a monohydric alcohol.

11. The fluid of claim 9,wherein said alcohol is a polyhydric alcohol.

12. In homogeneous hydraulic fluids of the class described, acomposition essentially consisting of from about 20% to about 72.5% by volume of 2, l'-dimethyl 'sulfolane, and as the balance a mixture of castor oil and an organic solvent.

13. The composition according to claim 1 which also contains a minor but efiective amount of a corrosion inhibitor.

v 14. The composition according to claim 5 which also contains a minor but effective amount of a corrosion inhibitor.

15. The composition according to claim 9 which also contains a minor but effective amount of a corrosion inhibitor.

16. The composition according to claim 12 t which also contains a minor but effective amount of a corrosion inhibitor.

ALVA V. 

